JP2002161912A - Manufacturing method of fluid bearing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a liquid-bearing unit in which air is hard to remain even if a concavity is in a shaft end. SOLUTION: In order to manufacture a spindle motor having an integrated flange 15 in one end and equipping a shaft 13 with a center hole 20 on the end, a sleeve 12, and a cup-shape housing 10, fill lubricant in the center hole 20 under the condition of the end of the shaft 13, where a flange 15 is provided, facing up and lubricate said facing-up plane. Next, mount the housing 10 on the shaft 13 and insert the shaft 13 into a cylinder 11a until the lubricant lubricating on said facing-up plane contacts with a counter plate 16. Then, move and insert the sleeve 12 into the cylinder 11a by inserting the shaft 13 through the sleeve 12. After that, fix the sleeve 12 on the inside peripheral surface of the cylinder 11a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information device,
The present invention relates to a method of manufacturing a hydrodynamic bearing device used for video equipment, office machines, and the like, and more particularly to a method of manufacturing a hydrodynamic bearing device optimal for a magnetic disk device (hereinafter referred to as an HDD), an optical disk device, and the like.

[0002]

2. Description of the Related Art Conventional hydrodynamic bearing devices of this type include:
For example, there is an HDD spindle motor as shown in FIG. This is a cylindrical part 10 erected on a base 101.
A cylindrical housing 100 having a bottom plate 100a is inserted inside 1a, and these are integrally fixed. A cylindrical sleeve 102 is inserted into the inner peripheral surface of the housing 100 and is integrally fixed.

Further, a shaft 103 is rotatably inserted through the sleeve 102. An inverted cup-shaped hub 104 is integrally attached to the upper end of the shaft 103, and a disk-shaped thrust plate 105 is fixed to the lower end of the shaft 103 by press-fitting. This thrust plate 10
5 are the thrust receiving surfaces 10 of the thrust fluid bearing S.
5 s and 105 s. The lower end surface of the sleeve 102, which is a mating member, faces the upper thrust receiving surface 105s via a fluid bearing clearance of the thrust fluid bearing S, and the lower end surface of the sleeve 102 is opposed to the thrust bearing surface 102s of the thrust fluid bearing S. Have been.

On the lower thrust receiving surface 105s,
The upper surface of the bottom plate 100a of the housing 100, which is the mating member, opposes through the fluid bearing clearance of the thrust fluid bearing S, and the upper surface of the bottom plate 100a is the thrust bearing surface 100s of the thrust fluid bearing S. The thrust receiving surfaces 105s, 105s and the thrust bearing surface 102
s and 100s are provided with a herringbone-shaped or spiral-shaped groove for generating dynamic pressure (not shown) to constitute a thrust fluid bearing S.

[0005] Further, a pair of radial receiving surfaces 103r, 103r are formed on the outer peripheral surface of the shaft 103 at an interval above and below. Further, on the inner peripheral surface of the sleeve 102, the radial bearing surfaces 103r, 103r are opposed to the radial bearing surfaces 103r via the fluid bearing clearance of the radial fluid bearing R.
r and 102r are formed. Then, the radial receiving surfaces 103r, 103r and the radial bearing surfaces 102r, 102r
The radial fluid bearings R, R are provided with at least one of herringbone-shaped or spiral-shaped dynamic pressure generating grooves 107, 107.

A stator 108 is fixed to the outer peripheral surface of the housing 100, and a drive motor M is formed facing the rotor magnet 109 fixed below the inner peripheral surface of the hub 104 via a gap. The shaft 103 and the hub 104 are integrally rotated by the drive motor M. When the shaft 103 rotates, dynamic pressure is generated in a small amount of lubricant filled in the fluid bearing clearances of the fluid bearings S and R by the pumping action of the dynamic pressure generating grooves of the thrust fluid bearing S and the radial fluid bearing R. Thus, the shaft 103 is not in contact with the inner peripheral surface of the sleeve 102 and the upper surface of the bottom plate 100a and is supported.

In such a conventional spindle motor, the thrust plate 105 is not formed integrally with the shaft 103, but is formed separately from the shaft 103. That is, after processing the shaft 103, the thrust plate 105 is attached to the shaft 103. In the case of a shaft with a flange (a shaft and a thrust plate are integrally formed), a center hole necessary for grinding the outer peripheral surface of the shaft serving as a bearing surface is provided on the end surface of the shaft. Must be provided. However, in the case of a rod-shaped shaft (straight shaft) having no flange portion as described above, grinding can be performed using a centerless grinding machine or the like. No need to provide.

[0008]

In recent years, HDDs have been required to have higher recording densities, and the width of tracks for recording information has become narrower. Therefore, the use of fluid bearings with high rotational accuracy has been studied. ing. Further, HDDs mounted on portable devices such as notebook computers are required to be thinner and have excellent portability (800
There is a demand for a hydrodynamic bearing device having high shock resistance (G or more) and high reliability (unstable vibration hardly occurs even when the use environment changes).

As a method for realizing the reduction in thickness, there is a method of reducing the height of the apparatus by reducing the thickness of the thrust plate 105. However, when the thickness of the thrust plate 105 is reduced, the fixing strength when the thrust plate 105 is pressed into the shaft 103 tends to decrease. Therefore, if a large impact is applied to the spindle motor during transportation or the like, the thrust plate 105 may fall off the shaft 103.

As a method for solving such inconvenience,
There is a method of integrally forming the shaft and the thrust plate. If the shaft and the thrust plate are integrated, there is no danger of falling off even if an impact is applied. However, in a shaft having such a flange portion, in order to grind the outer peripheral surface of the shaft serving as a bearing surface using a grinder or the like, it is necessary to provide a center hole in the end surface of the shaft as described above. There is. Then, the shaft can be ground using a cylindrical grinder, an angular grinder, or the like.

On the other hand, the method of filling a lubricant in the conventional manufacturing of a spindle motor is as follows. First, a lubricant is injected into the housing 100 (on the upper surface of the bottom plate 100a). Subsequently, the shaft 103 is inserted into the housing 100, and the plane of the thrust plate 105 (the lower plane in FIG. 3) faces the upper surface of the bottom plate 100a as shown in FIG. Then, the housing 1 into which the shaft 103 is inserted.
00 and the sleeve 102 are relatively moved, the sleeve 102 is inserted into the housing 100 while the shaft 103 is inserted through the sleeve 102, and the sleeve 102 is fixed to the housing 100 by press fitting.

Therefore, if the shaft is provided with a center hole at the end face, if the lubricant is filled by such a method, the air is trapped in the center hole and air may remain inside the spindle motor. There is. for that reason,
In an operating environment where the air pressure and temperature change, the residual air expands and moves and turns within the fluid bearing clearance, so that unstable vibration is likely to occur during rotation.

In other words, when the shaft and the thrust plate are integrally formed in order to reduce the thickness and improve the impact resistance, a concave portion such as a center hole is provided on the end surface of the shaft, so that the conventional manufacturing method is used. In the case of (the method of filling the lubricant), air remains in the concave portion, and the spindle motor is liable to generate unstable vibration due to a change in the use environment, resulting in a problem that reliability is poor.

Therefore, the present invention solves the above-mentioned problems of the conventional method of manufacturing a hydrodynamic bearing device, and manufactures a hydrodynamic bearing device in which air does not easily remain inside even when a shaft has a concave portion at its end face. Provide a way.

[0015]

In order to solve the above-mentioned problems, the present invention has the following arrangement. That is, the manufacturing method of the hydrodynamic bearing device of the present invention includes a shaft having an integrally formed flange portion at one end, a sleeve facing the shaft via a fluid bearing clearance of a radial fluid bearing, and A cup-shaped housing to be inserted, and the shaft has a concave portion on an end surface of the both end surfaces on the side where the flange portion is provided, and both flat surfaces of the flange portion are fluid bearings of a thrust fluid bearing. Through the gap,
When manufacturing the hydrodynamic bearing device respectively opposed to the bottom plate portion and the sleeve provided in the housing, the shaft is placed in a state in which the end surface on the side where the flange portion is provided faces upward, and then the inside of the concave portion is formed. Filling a lubricant, furthermore, a first step of placing the lubricant on the flat surface facing upward, and covering the housing on the shaft with its opening facing downward, A second step of inserting the shaft into the housing until the lubricant placed on the upwardly facing plane contacts the bottom plate portion, and the lubricant on at least the outer peripheral portion of the downwardly facing plane Is reached, the housing in which the shaft is inserted and the sleeve are relatively moved, and the sleeve is inserted into the housing while the shaft is inserted through the sleeve. Characterized in that it and a third step of filling the lubricant to the fluid bearing clearance of the radial fluid bearing interposed between said shaft and.

When the shaft and the thrust plate are integrally formed, a concave portion such as a center hole necessary for machining the shaft is provided on the end face of the shaft. For example, when the hydrodynamic bearing device is assembled, air is trapped in the recess, and there is no possibility that air remains in the hydrodynamic bearing device. Therefore, even in a use environment in which the atmospheric pressure and the temperature change, unstable vibration hardly occurs during rotation.

Therefore, the obtained hydrodynamic bearing device is thin, has excellent impact resistance, and has high reliability.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the hydrodynamic bearing device according to the present invention will be described in detail with reference to the drawings. FIG.
Is a fluid dynamic bearing device according to an embodiment of the present invention.
It is a longitudinal section of the spindle motor for D. First, the structure of the spindle motor will be described.

This spindle motor comprises a shaft 13 to which a hub 14 is fixed and a sleeve 12 through which the shaft 13 is inserted. A radial fluid bearing R is interposed between the shaft 13 and the sleeve 12. Have been. Also, a flange 15 is provided at one end of the shaft 13, and the flange 1 is provided.
5 and a thrust fluid bearing S is provided between the sleeve 12 and the counter plate 16 opposed thereto.

The base 11 to which the sleeve 12 is fixed
A stator 18 is fixed to the outer peripheral surface of the cylindrical portion 11a, and a driving motor M is formed so as to face the rotor magnet 19 fixed to the inner peripheral surface of the hub 14 via a gap. When the hub 14 and the shaft 13 are integrally rotated by the drive motor M, the shaft 13 is rotatably supported on the sleeve 12 by the thrust fluid bearing S and the radial fluid bearing R. I have.

The cylindrical part 11a of the base 11 and the counter plate 16 constitute a housing which is a constituent element of the present invention, and the counter plate 16 corresponds to a bottom plate part which is a constituent element of the present invention. Next, the structure of the spindle motor of the present embodiment as described above will be described in more detail.

A cylindrical sleeve 12 is inserted inside a cylindrical portion 11a erected at the center of the base 11, and these are integrally fixed. Sleeve 1
2, a shaft 13 is rotatably inserted. The material of the shaft 13 is not particularly limited as long as it is a material having high hardness and excellent corrosion resistance. For example, a martensitic stainless steel or an austenitic stainless steel is subjected to a heat treatment to harden the surface. Or a hardened copper alloy surface-treated by plating or surface treatment with a diamond-like carbon (DLC) film, and a copper alloy having high hardness.

The upper end portion 13a of the shaft 13 has a smaller diameter than the other portion. The small upper end portion 13a is press-fitted into a hole provided at the center of a shallow inverted cup-shaped hub 14 so as to be pressed. And the hub 14 are integrally fixed. Since the lower surface of the hub 14 abuts on the upper end surface 13b of the large-diameter other portion formed at the boundary between the small-diameter upper end portion 13a and the large-diameter other portion, the shaft 13 and the hub 14 are sufficiently separated from each other. With sufficient strength to ensure high impact resistance.

A disk-shaped flange 15 is formed integrally with the shaft 13 at the lower end of the shaft 13 protruding from the lower end of the sleeve 12. Since the flange portion 15 is formed integrally with the shaft 13, there is no possibility that the flange portion 15 will fall off the shaft 13 even if it receives a strong impact (excellent impact resistance). In addition, since the height of the apparatus can be reduced by reducing the thickness of the flange portion 15, the thickness of the spindle motor can be easily reduced.

It should be noted that the flange portion 1 of the both end surfaces of the shaft 13
A center hole 20 is provided on the end face on the side where 5 is provided. Note that the center hole 20 corresponds to a concave portion which is a constituent element of the present invention. Such a center hole 20
Is not necessary for straight shafts, but for shafts with flanges, grinding the outer peripheral surface of
This is necessary because the grinding is performed using a grinding machine such as a cylindrical grinding machine or an angular grinding machine.

The lower surface of the flange portion 15 is opposed to the upper surface of a counter plate 16 attached to the central portion of the base 11, and the opposed surfaces are in contact when the spindle motor is stopped. Also, the upper surface of the flange portion 15
It faces the lower end surface of the sleeve 12. Flange part 15
Are formed as thrust receiving surfaces 15s, 15s. The sleeve 12 opposes the upper thrust receiving surface 15s via the clearance fluid bearing of the thrust fluid bearing S.
And the upper surface of the counter plate 16 which faces the lower thrust receiving surface 15s via the clearance fluid bearing of the thrust fluid bearing S, respectively, with the thrust bearing surface 12s.
And 16s, and the opposing thrust receiving surfaces 15s, 1
At least one of the 5s and the thrust bearing surfaces 12s and 16s is provided with, for example, a herringbone-shaped groove for generating a dynamic pressure (not shown) to constitute a thrust fluid bearing S.

In particular, the herringbone-shaped dynamic pressure generating groove provided on the thrust receiving surface 15s or the thrust bearing surface 16s has a diameter such that the groove length on the outer peripheral side from the groove top is shorter than the groove length on the inner peripheral side from the groove top. It is preferable to have a slightly asymmetric groove pattern facing outward in the direction. Then, since the pumping action generated by the rotational drive is smaller on the outer peripheral side than on the groove top than on the inner peripheral side, the lubricant is sent out from the central part toward the outer peripheral part.

The method of forming the grooves for generating the dynamic pressure on both planes (thrust receiving surfaces 15s, 15s) of the flange portion 15 is not particularly limited.
Etching and the like. The coining process, which is plastic working, is a method of stamping the dynamic pressure generating groove by pressing a mold against the flange portion 15 using a press or the like. Cost.

On the other hand, a pair of radial receiving surfaces 13r, 13r are formed on the outer peripheral surface of the shaft 13 at intervals in the axial direction, and a pair of radial receiving surfaces 13r, 13r are provided with the fluid of the radial fluid bearing R. Radial bearing surfaces 12r, 12r facing each other via a bearing clearance are formed on the inner peripheral surface of the sleeve 12. And, the radial bearing surfaces 12r, 1
The radial fluid bearings R, 2 are provided on the 2r with hydrodynamic pressure generating grooves 17, 17 having a substantially U-shaped herringbone shape. However, the dynamic pressure generating grooves 17, 17 may be provided on the radial receiving surfaces 13r, 13r, or may be provided on both the radial receiving surfaces 13r, 13r and the radial bearing surfaces 12r, 12r.

The processing method for providing the dynamic pressure generating groove 17 is not particularly limited, and the same conventional method as described above is employed. When the dynamic pressure generating groove 17 is formed on the radial bearing surface 12r, that is, on the inner peripheral surface of the sleeve 12, the dynamic pressure generating groove 17 can be formed by plastic working such as ball rolling or cutting with a cutting tool which is excellent in mass productivity. Therefore, it is preferable. Ball rolling is a method in which a rolling jig in which a plurality of steel balls are held in a hollow outer cylinder fitted on the outer periphery of a shaft is pressed into the sleeve 12 to perform processing.

That is, after the sleeve 12 is cut on a lathe, the rolling jig is pushed into the sleeve 12 and relatively moved while slowly rotating the main shaft of the lathe forward and backward, thereby forming a herringbone shape (substantially) on the inner peripheral surface. The groove processing is performed in the shape of a letter (shape), and thereafter, finishing processing such as finishing cutting or ball threading for removing a bulging portion around the groove is performed as necessary. Needless to say, the sleeve 1 is not fixed on the lathe but fixed by rotating the rolling jig right and left using the rolling device.
2 to form a herringbone groove.

Dynamic pressure generating grooves 17, 1 provided at two locations
It is preferable that the groove 7 located on the outside air side be an inward asymmetric groove pattern whose groove length is slightly shorter on the inner side than on the outside air side for the following reasons. In other words, since the pressure that pushes the lubricant in from the outside air side to the inside acts as the shaft 13 rotates (pump-in), the lubricant in the fluid bearing clearance of the radial fluid bearing R is centrifuged by the rotation of the shaft 13. It is prevented from being scattered to the outside by the force.

This will be described in more detail. The dynamic pressure generating groove 17 is composed of a plurality of substantially rectangular grooves arranged at predetermined intervals along the circumferential direction of the shaft 13. 2
Of the dynamic pressure generating grooves 17 provided at the two locations, the dynamic pressure generating groove 17 (the upper dynamic pressure generating groove 17 in FIG. 1) located on the outside air side has an axially asymmetric pattern. Shape. The other dynamic pressure generating groove 17 (FIG. 1)
In the above, the pattern of the lower dynamic pressure generating groove 17) is formed in a shape symmetrical in the axial direction.

That is, in the dynamic pressure generating groove 17 located on the outside air side, the width from the bent portion to the end on the outside air side of the width in the axial direction of the substantially U-shaped groove is set to the inside from the bent portion. Shall be larger than the width up to the end. In the present embodiment, the outside air side is opposite to the side of the shaft 13 facing the outside air of the spindle motor (upward in FIG. 1), that is, the side on which the thrust fluid bearing S is provided. It means side. The inside means the side opposite to the outside air side, that is, the side on which the thrust fluid bearing S is provided.

Further, in order to reduce bubbles from being caught in the lubricant in the fluid bearing clearances of the thrust fluid bearing S and the radial fluid bearing R during rotation, it is necessary to provide the thrust fluid bearings S and the radial fluid bearing R with dynamic fluid. It is desirable that the pressure generation groove has a groove angle (an angle formed with respect to the rotation direction) of 30 ° or less, preferably 25 ° or less, and the number of grooves is 10 or more, preferably 12 or more.

In particular, when the bearing width of the herringbone-shaped dynamic pressure generating groove 17 provided in the radial fluid bearing R (the axial width of the dynamic pressure generating groove 17) is smaller than the shaft diameter, the groove angle is reduced. It is desirable that the angle is 25 ° or less, and the number of grooves is 12 or more, preferably 16 or more. When air bubbles are caught in the lubricant, unstable vibration during rotation is caused, and rotation accuracy is likely to be deteriorated.

In order to reduce the torque of the spindle motor, the inner circumferential surface of the sleeve 12 (the outer circumferential surface of the shaft 13 or the inner circumferential surface of the sleeve 12 may be interposed between the upper and lower radial fluid bearings R, R). The clearance groove may be provided on both the surface and the outer peripheral surface of the shaft 13). The clearance groove may be formed of a tapered circumferential groove whose clearance decreases toward the fluid bearing clearance of the radial fluid bearing R.

Further, the axial position of the rotor magnet 19 and the stator 18 constituting the drive motor M is slightly shifted, so that an axial attraction force acts, and the load is mainly shared on the lower end surface side of the sleeve 12. In addition, by designing the effective area of the lower thrust receiving surface 15 s of the flange portion 15 to be smaller than the effective area of the upper thrust receiving surface 15 s (designing the effective bearing diameter to be smaller), May be reduced. Then, the power consumption of the spindle motor can be reduced.

Next, the lubricant reservoir 22 will be described. A clearance is interposed between the outer peripheral surface of the sleeve 12 and the inner peripheral surface of the cylindrical portion 11a, and the clearance forms a lubricant reservoir 22. The outer peripheral surface of the sleeve 12 forming the inner surface of the lubricant reservoir 22 is a tapered surface 24,
As a result, the clearance of the lubricant reservoir 22 gradually decreases toward the lower thrust fluid bearing S.

However, the tapered surface 24 is not always formed on the outer peripheral surface of the sleeve 12 and may be formed on the inner peripheral surface of the cylindrical portion 11a, or the outer peripheral surface of the sleeve 12 and the inner peripheral surface of the cylindrical portion 11a. May be formed on both.
Such a lubricant reservoir 22 is provided so as to form an axial slit in a fitting surface between the sleeve 12 and the cylindrical portion 11a.
An opening is provided at the upper end surface of the sleeve 12 to communicate with the outside air.
The number of the lubricant reservoirs 22 may be one or more.

The lubricant is held in the lubricant reservoir 22 by capillary action based on surface tension. This lubricant is sucked into the narrow gap by the surface tension, while the residual air bubbles entrained at the time of assembly are separated into the wide gap (upper part) and discharged from the portion opened at the upper end surface of the sleeve 12. Is done. Therefore, the lubricant without bubbles is reliably supplied to each fluid bearing clearance.

An opening is formed at the lower end of the lubricant reservoir 22 toward an annular clearance formed between the outer peripheral surface 15a of the flange portion 15 and the inner peripheral surface of the cylindrical portion 11a which is a member opposed thereto. A lubricant supply passage 25 is provided. The opening of the lubricant supply passage 25 communicating with the fluid bearing clearance of the thrust fluid bearing S is substantially equal to or slightly larger than the fluid bearing clearance of the thrust fluid bearing S. The lubricant is supplied from the lubricant supply passage 25 by the capillary action based on the thrust fluid bearing S.
Is easily introduced into the fluid bearing clearance.

In this embodiment, the entire outer peripheral surface of the sleeve 12 is a tapered surface 24, a part of the tapered surface 24 of the lubricant reservoir 22 is a lubricant supply passage 25, and the outer peripheral surface 15 a of the flange 15 is The tapered surface 24 is directly communicated with an annular clearance formed between the tapered surface 24 and the inner peripheral surface of the portion 11a. However, the upper part of the outer peripheral surface of the sleeve 12 is a tapered surface 24, and the lower part is a surface parallel to the inner peripheral surface of the cylindrical portion 11 a, and the clearance formed by this parallel surface forms the lubricant supply passage 25. It may have a structure.

Next, the structure of the upper end (outside air side) of the inner peripheral surface of the sleeve 12 will be described in detail. Sleeve 1
Almost the entire inner peripheral surface of the inner peripheral surface of the sleeve 12 faces the outer peripheral surface of the shaft 13.
It is chamfered as shown in FIG. This allows
The uppermost portion (outside air side) of the clearance formed between the outer peripheral surface of the shaft 13 and the inner peripheral surface of the sleeve 12 has a tapered shape in which the clearance gradually increases toward the outer air side (upward). Has become. At this time, the angle formed by the tapered shape, that is, the inclined surface 12a of this chamfered portion and the shaft 13
Is defined as α. As can be seen from FIG. 1, the groove 17 for dynamic pressure generation is not provided in the tapered clearance, and therefore, the tapered clearance is formed by the fluid in the radial fluid bearing R. There is no bearing clearance.

The angle α formed by the tapered shape is
Is larger than the angle formed between the tapered surface 24 and the inner peripheral surface of the cylindrical portion 11a (hereinafter, referred to as the inclination angle of the tapered surface 24). With such a configuration, since the surface tension acts strongly on the narrower gap, the lubricant is more strongly sucked into the lubricant reservoir 22 than the tapered gap of the chamfered portion, The liquid level of the lubricant located at the chamfered portion can be lowered and can be maintained below the chamfered portion.

Further, the volume of the lubricant reservoir 22 is
Of the gap formed between the outer peripheral surface of the sleeve 3 and the inner peripheral surface of the sleeve 12 has a tapered shape at the uppermost portion (that is, the inclined surface 12a of the chamfered portion,
A portion of the outer peripheral surface of the shaft 13 facing the inclined surface 12a,
If the volume is larger than the volume of the portion surrounded by, the extra lubricant will be held in the lubricant reservoir 22.

Therefore, even if the amount of the injected lubricant is excessive or insufficient, the possibility that the lubricant is scattered to the outside or the lubricant in the fluid bearing clearance is depleted during a long-term use is reduced. The long-term reliability of the spindle motor is excellent. In order to sufficiently exhibit the above-described effects, it is preferable that the inclination angle of the tapered surface 24 is 0 ° or more and less than 45 °, and the angle α formed by the tapered shape is 45 ° or more. In particular, the inclination angle of the tapered surface 24 is set to 10 °
When the following conditions are satisfied, the above-mentioned effect is more sufficiently exhibited. In addition, in order to suck and hold the excess lubricant in the lubricant reservoir 22 by surface tension, it is practically preferable that the angle α formed by the tapered shape is larger than the inclination angle of the tapered surface 24 by 15 ° or more. .

In order to widen the bearing span, which is the distance between the two radial fluid bearings R, within the determined device height, the outer peripheral surface of the shaft 13 and the inner peripheral surface of the sleeve 12 are not The length of the tapered portion of the gap formed between them, that is, the axial width of the inclined surface 12a of the chamfered portion needs to be smaller.

On the other hand, since it is necessary to retain as much excess lubricant as possible in the lubricant reservoir 22, the angle α formed by the tapered shape is 45 ° or more, and the axial width of the inclined surface 12a is 1 mm or less, preferably 1 mm or less. It is desirable to set it to 0.5 mm or less. Further, in order to increase the long-term reliability, it is necessary to secure a sufficient amount of the lubricant that can be held in the lubricant reservoir 22, so that the width of the tapered surface 24 in the axial direction is
It is preferable that the width a is twice or more the axial width of a.

Also, the width (radial width) of the widest part of the tapered shape of the chamfered part
Is larger than the width (radial width) of the widest part of the lubricant reservoir 22, and is held by the lubricant level located in the chamfered portion and the lubricant reservoir 22. The liquid level of the lubricant is at a position where the surface tension is balanced. Accordingly, the liquid level of the lubricant located in the chamfered portion can be maintained below the chamfered portion, and the lubricant is prevented from scattering from the chamfered portion to the outside with the rotation.

In this embodiment, the slope 12
a is provided on the inner peripheral surface of the sleeve 12 (that is,
The chamfered portion may be provided on the inner peripheral surface of the sleeve 12), may be provided on the outer peripheral surface of the shaft 13, or may be provided on both the inner peripheral surface of the sleeve 12 and the outer peripheral surface of the shaft 13. When the inclined surface 12a is provided on the outer peripheral surface of the shaft 13,
It is provided on the part closest to the outside air among the parts facing the inner peripheral surface of the sleeve 12.

An oil repellent (having a property of repelling a lubricant) is applied to the inclined surface 12a of the chamfered portion of the sleeve 12 and a portion of the outer peripheral surface of the shaft 13 facing the inclined surface 12a. When the oil-repellent treatment is performed, the lubricant is repelled to the oil-repelled portion, so that when the spindle motor stops and rotates, the lubricant exceeds the oil-repellent portion (such as the chamfered portion). Leaks out
It can be more effectively prevented.

Next, a method for manufacturing (assembling) the above-described spindle motor will be described in the order of steps. (1) First Step First, the shaft 13 is set in a state where the end surface on the side where the flange portion 15 is provided faces upward. Then, the center hole 20 is filled with a lubricant, and the lubricant is placed on a plane facing upward.

(2) Second Step The base 11 (that is, the housing 10) to which the counter plate 16 is attached is placed on the shaft 13 with the opening of the cylindrical portion 11a facing downward, and the above-mentioned flat surface facing upward The shaft 13 is inserted into the housing 10 (the cylindrical portion 11a) until the lubricant placed on the
Insert

Then, the lubricant placed on the upwardly directed plane reaches at least the outer peripheral portion of the downwardly directed plane via the outer peripheral surface 15a of the flange portion 15. However, in the first step, if the amount of the lubricant placed on the plane facing upward is small, the lubricant may not reach the outer peripheral portion of the plane facing downward. In this case, the lubricant is supplied from the outside to the outer peripheral portion so that the lubricant reaches at least the outer peripheral portion of the flat surface facing downward.

(3) Third Step By moving the sleeve 12, the sleeve 12 is inserted into the cylindrical portion 11a (housing 10) while the shaft 13 is inserted through the sleeve 12, and thereafter, the sleeve 12 is moved to the cylindrical portion 11a. Is fixed to a predetermined position on the inner peripheral surface. At this time,
By moving the housing 10 instead of the sleeve 12,
The sleeve 12 may be inserted into the cylindrical portion 11a, or both the sleeve 12 and the housing 10 may be moved to insert the sleeve 12 into the cylindrical portion 11a.

When the sleeve 12 is inserted into the cylindrical portion 11a, the end surface (the lower end surface in FIG. 1) of the sleeve 12 is
In contact with the lubricant reaching at least the outer peripheral portion of the flat surface facing downward, the lubricating lubricant is inserted into the fluid bearing clearance of the radial fluid bearing R interposed between the inner peripheral surface of the sleeve 12 and the outer peripheral surface of the shaft 13. The agent spreads and fills the fluid bearing clearance.

If the lubricant flows out of the fluid bearing clearance beyond the chamfered portion of the sleeve 12, the lubricant is removed by a method such as wiping.
After the second step, the housing 1 into which the shaft 13 has been inserted.
0 may be turned upside down so that the opening of the cylindrical portion 11a faces upward, and then the process may proceed to the next third step.

In such a method, the center hole 20
The spindle motor can be assembled without air remaining in the spindle motor. Therefore, even in a use environment in which the atmospheric pressure and the temperature change, unstable vibration hardly occurs during rotation. In addition, since the lubricant gradually spreads and fills the clearances of the respective fluid bearings by using the surface tension, there is little possibility that air bubbles may be trapped inside the spindle motor (in the vicinity of the fluid bearing clearances) during assembly. .

It should be noted that even a small amount of residual air bubbles may cause unstable vibration. Therefore, in order to further ensure the deaeration of the air bubbles, if necessary, use a lubricant which has been previously vacuum degassed or used as a lubricant. After the filling, the spindle motor may be placed in a vacuum chamber to perform vacuum degassing. The injected lubricant is
In addition to filling the clearances of the thrust fluid bearing S and the radial fluid bearing R with the surface tension, excess lubricant is accumulated in the lubricant reservoir 22 via the lubricant supply passage 25, and the tapered surface is formed by capillary action based on the surface tension. 24. Therefore, even if the injection amount of the lubricant is excessive, there is no problem because the excess lubricant is stored in the lubricant reservoir 22. Further, even if the spindle motor is inverted during transportation or handling, the lubricant in the lubricant reservoir 22 does not flow out.

Further, since the size of the clearance of the lubricant reservoir 22 is reduced toward the lower lubricant supply passage 25 by the tapered surface 24, the lubricant scattered by the external impact is also required unless it flows out. Are naturally collected in the lubricant supply passage 25 having a narrow clearance in the lubricant reservoir 22. The air bubbles collected in the upper part (the larger one of the gaps) of the lubricant reservoir 22 are discharged from the portion opened to the upper end surface of the sleeve 12.

In the spindle motor manufactured in this manner, the drive motor M causes the hub 14 and the shaft 13 on which a magnetic disk (not shown), which is a rotating body, is mounted on the outer periphery to be integrally rotated and driven. Due to the pumping action of the dynamic pressure generating grooves of the fluid bearing S and the radial fluid bearing R, dynamic pressure is generated in the lubricant filled in the fluid bearing clearances of the fluid bearings S and R, and the shaft 13
And it comes out of contact with the counter plate 16 and is supported. Since the magnetic disk is screwed with a clamp member, the magnetic disk is fixed to the hub 14 with sufficient strength to ensure sufficient impact resistance.

If the lubricant retained in the fluid bearing clearance gradually evaporates or scatters and runs short over a long period of time, the lubricant is retained in the lubricant reservoir 22 by capillary action based on surface tension. The lubricated lubricant is sucked into the narrower gap while being guided by the tapered surface 24 according to the shortage, and is replenished until the lubricant is filled in the fluid bearing clearance. That is, as the lubricant in the fluid bearing clearance decreases, the lubricant is sucked by the capillary bearing via the lubricant supply passage 25 into the fluid bearing clearance having a smaller clearance, and the surface tension of the tapered surface 24 of the lubricant reservoir 22 is balanced. And stabilized. Thus, the lubricant is automatically replenished by the reduced amount of the lubricant.

Next, the hydrodynamic bearing unit will be described. In the spindle motor described above, when the cylindrical portion 11a and the counter plate 16 are formed integrally (that is, when the housing 10 is formed integrally), a portion composed of the sleeve 12, the shaft 13, and the housing 10 is formed. Since the hydrodynamic bearing unit is integrally formed and the integrated hydrodynamic bearing unit can be incorporated into the spindle motor at a time, the manufacture and production of the spindle motor
Assembly becomes very easy.

A fluid bearing unit is manufactured in advance by a bearing manufacturer (assembly and injection of lubricant).
Since it can be completed into a spindle motor by a spindle motor manufacturer, there is an advantage that it is easy to share production. FIG. 2 shows an embodiment of such a hydrodynamic bearing unit. The description of the same parts as those of the spindle motor shown in FIG. 1 will be omitted, and only different parts will be described. In FIG. 2, the same or corresponding parts as those in FIG. 1 are denoted by the same reference numerals as those in FIG.

This fluid bearing unit comprises a shaft 13 having an integrally formed flange portion 15 at one end,
And a cup-shaped housing 10 in which the sleeve 12 is inserted. A radial fluid bearing R is interposed between the shaft 13 and the sleeve 12, and both flat surfaces of the flange portion 15, the lower end surface of the sleeve 12 opposed thereto and the bottom plate portion of the housing 10 corresponding to the counter plate. Between 10a
A thrust fluid bearing S is provided.

Although the fluid bearing unit shown in FIG. 2 does not have the lubricant reservoir 22, it is needless to say that the lubricant reservoir 22 may be provided similarly to the above-described spindle motor. If the housing 10 of such a hydrodynamic bearing unit is mounted on a base and a hub is mounted on the upper end of the shaft 13, a spindle motor is completed. Note that the present embodiment is an example of the present invention, and the present invention is not limited to the present embodiment.

For example, the spindle motor may be a sleeve fixed-shaft rotating type or a shaft fixed-sleeve rotating type. Further, the structure of the fluid bearing, the pattern of the groove for generating dynamic pressure, the detailed structure of the spindle motor, and the like are not limited to the present embodiment, and if necessary, if the object of the present invention can be achieved. It can be changed as appropriate.

Further, the groove for generating dynamic pressure is not limited to a herringbone shape or a spiral shape, but may be any groove pattern as long as it functions as a hydrodynamic bearing.
In addition, etching, electrolytic etching, plastic processing, cutting, laser processing, ion beam processing, shot blast, or the like can be applied to the groove according to the material and the required accuracy.

Further, the material of the members constituting the spindle motor such as the shaft 13 and the sleeve 12 is not particularly limited, and metals (stainless steel, copper alloy, Materials such as aluminum alloys), sintered metals, sintered oil-impregnated metals, plastics, and ceramics can be used without any problems. That is,
It may be a combination of stainless steel or copper alloy,
A combination of dissimilar metals such as iron and copper alloy, iron and aluminum alloy, or a combination of metal and plastic may be used. Of course, a surface treatment such as plating or a DLC film (diamond-like carbon coating) may be applied to the fluid bearing surface as necessary to improve the slidability at the time of starting and stopping.

When the sleeve 12 and the flange portion 15 are made of a combination of copper alloys having different hardnesses, for example, beryllium copper or aluminum bronze having high hardness for the sleeve 12 and lead bronze or phosphor bronze for the flange portion 15. Slidability and cutting workability can be satisfied. Or, conversely, a copper alloy having high hardness may be used for the flange portion 15. In this case, it is preferable to provide a groove for generating a fluid shunt on the fluid bearing surface of lead bronze or phosphor bronze having a low hardness because the mating member is less likely to be damaged.

Further, in this embodiment, the spindle motor has been described as an example of the hydrodynamic bearing device, but the present invention can be applied to various other hydrodynamic bearing devices.

[0073]

As described above, according to the manufacturing method of the hydrodynamic bearing device of the present invention, even when the shaft is provided with the concave portion on the end face, the air hardly remains inside. Therefore, the obtained hydrodynamic bearing device is thin and excellent in impact resistance, and is unlikely to generate unstable vibration even when the use environment changes.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a spindle motor which is an embodiment of a hydrodynamic bearing device according to the present invention.

FIG. 2 is a longitudinal sectional view showing an embodiment of the hydrodynamic bearing unit.

FIG. 3 is a longitudinal sectional view of a conventional spindle motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Housing 10a Bottom plate part 11 Base 11a Cylindrical part 12 Sleeve 13 Shaft 15 Flange part 16 Counter plate 20 Center hole R Radial fluid bearing S Thrust fluid bearing

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02K 15/14 H02K 15/14 A // G11B 19/20 G11B 19/20 EF term (Reference) 3J011 AA07 BA04 BA06 BA08 CA02 DA02 JA02 KA02 KA03 KA05 MA21 5D109 BB01 BB05 BB12 BB18 BB21 BB22 5H605 AA00 BB05 BB19 CC04 CC05 DD03 EB02 EB06 EB21 5H607 BB01 BB17 CC01 DD01 DD02 DD03 DD16 GG01 GG01 GG01 GG01 GG01 GG01 GG01 GG01 GG01 GG01 GG01 GG01 GG01 GG01 GG01 GG01 GG01 GG01 GG02

Claims (1)

[Claims] 1. A shaft having an integrally formed flange portion at one end, a sleeve facing the shaft via a fluid bearing clearance of a radial fluid bearing, a cup-shaped housing into which the sleeve is inserted, and The shaft is provided with a concave portion on an end surface of the both end surfaces on the side where the flange portion is provided, and both flat surfaces of the flange portion are formed through a fluid bearing clearance of a thrust fluid bearing. When manufacturing a hydrodynamic bearing device that respectively faces the bottom plate portion and the sleeve that are provided, after the shaft is in a state where the end surface on the side where the flange portion is provided faces upward, a lubricant is filled in the concave portion. Filling,
Further, a first step of placing a lubricant on the upwardly-facing plane, and covering the housing on the shaft with the opening thereof facing downward, A second step of inserting the shaft into the housing until the lubricant placed thereon comes into contact with the bottom plate, and in a state where the lubricant reaches at least the outer peripheral portion of the flat surface facing downward, The housing and the sleeve in which the shaft is inserted are relatively moved, and the sleeve is inserted into the housing while the shaft is inserted through the sleeve, so that the sleeve is interposed between the sleeve and the shaft. And a third step of filling the lubricant in a fluid bearing clearance of the radial fluid bearing.